Mercury can be present in trace amounts in all types of hydrocarbon streams such as crude oils. The amount can range from below the analytical detection limit to several thousand ppbw (parts per billion by weight) depending on the source.
Methods have been disclosed to remove mercury from liquid hydrocarbon feed, specifically volatile mercury. It has been reported that mercury in crude oil is primarily in the form of volatile species, e.g., 90% Hg(0) and only 10% DMHg. See Wilhelm et al. Energy & Fuels 2006, 20, 180-186 (See Table 5 on page 184) (http://pubs.acs.org/doi/pdf/10.1021/ef0501391). In contrast, Tao et al. J. Anal. At. Spectrom., 1998, 13, 1085-1093 (http://pubs.rsc.org/en/content/articlepdf/1998/ja/a803369b) show in Table 8 that dialkylmercury species out-proportion elemental Hg in condensates and natural gas liquids.
U.S. Pat. No. 4,915,818 discloses a method of removing mercury from liquid hydrocarbons (natural gas condensate) by contact with a dilute aqueous solution of alkali metal sulfide salt, for reaction of the sulfur component with the mercury, where the mercury sulfur compounds precipitate and settle for subsequent recovery as a solid waste. U.S. Pat. No. 6,268,543 discloses a method for removing elemental mercury with a sulfur compound where mercury is removed as a solid. U.S. Pat. No. 6,350,372 discloses the removal of mercury from a hydrocarbon feed upon contact with an oil soluble or oil miscible sulfur compound U.S. Pat. No. 4,474,896 discloses using polysulfide based absorbents to remove elemental mercury from gaseous and liquid hydrocarbon streams.
There are also a number of commercially available processes and products for the removal of (volatile) elemental mercury from hydrocarbon streams including but not limited to ICI Synetix's Merespec™ fixed bed absorbents, UOP's HgSIV™ regenerative mercury removal adsorbents, and Johnson Matthey's Puraspec™ and Puracare™ granulated absorbents for the removal of mercury from naphtha and/or gaseous hydrocarbon streams. Adsorption technology does not work well for crude oils and condensates with low levels of mercury, and with primarily non-volatile mercury.
While aqueous sulfide treatments for crude oil result in removal of mercury from the crude oil, conventional processes are burdened by aqueous fluids containing spend sulfide solutions that must be discarded. There is further need for methods for removing mercury from crude oil using reagents that may be recycled and reused in the method.